The reason I ask is what happens If the first flight is late in arriving.
Ana5162 has a habit of being delayed.
I know there are other options but I'm on a tight budget and these flights are one of the cheapest.

If you misconnect Brussels Airlines will be responsible for getting you to Tokyo but that late your possible same day rebooking is very limited and would probably leave you in a hotel for the night and then on the next day.

It’s on a single ticket so it is Brussels Airlines that is responsible for getting you to Tokyo in case you can’t make the second flight.

I wouldn't do it. Even if you can check your luggage all the way through, a slight flight delay from MAN could spell disaster.

This is clearly a single ticket/PNR (otherwise the SN flight from MAN wouldn't have a NH flight No.) so there is no issue (unless you absolutely need to be in Japan the following day). If you misconnect at BRU SN will rebook you to fly to Japan the following day - either on NH232 the following day (if operated that day) or via FRA/MUC or any other LH group gateway. Depending on the reason for the delay of incoming flight you may even be able to collect EUR 600 as compensation for delay under EU Reg. 261/04. Go ahead and book!

If your luggage doesn't make it to Japan with you, go on a shopping spree for essential clothing and toiletries upon arrival and submit the receipts to SN for reimbursement later on.

Anyway, 1 hour is more than plenty of time to connect at BRU and for your luggage to be loaded on NH232; transferring at BRU is easy and doesn't take long so unless your inbound flight from MAN is seriously late, you will make it in time to the NH flight.

Taking a later flight is a disaster?

It is if the two flights are not booked together and the BRU to NRT flight is non-refundable.

Based on the screenshot provided, it's perfectly clear that this is a single itinerary that involves a codeshare flight. Multiple people have accurately pointed out that if the initial flight is delayed, the airline is still responsible for getting the OP to the final destination.

Missing the connecting flight could be described as anywhere between an annoyance and a major inconvenience. Calling a missed connection a "disaster" seems wildly hyperbolic.

True, but in this case it's pretty obvious that it's a single ticket.

On a side-point, why do airlines love selling these tight connections as the cheapest?
First off, if they are of the perspective time is money (that is why non-stop is more expensive than a connection) aren't tight connections better?
Or do they realize that sometimes they will miss their connection and be inconvenience, and business travellers cannot afford that?